This invention relates to a charging apparatus for use either in a local area network (LAN) or in a bridge apparatus interconnecting a plurality of local area networks.
Local area networks are recently more and more widely used. As a consequence, a bridge and a router have come into practical use in connecting the local area networks together into an internetwork. Various protocols are concurrently used in a network layer of the local area networks. Typical examples of the protocols used in the network layer are transmission control protocol/internet protocol (TCP/IP).
Under the circumstances, a multiprotocol router is developed in order to simultaneously deal with a plurality of protocols. A brouter is also developed as a particular bridge for a link layer alone so as to cope with packets which can not be processed in the network layer. An arrangement for interconnecting the local area networks, such as the bridge, the router, or the brouter, is herein called a bridge apparatus.
Along with a wider use of the local area networks, it has become practice to put the internetwork in operation on a commercial basis. In such a situation, a charging apparatus has become necessary for use either in the local area network or in a bridge apparatus in individually charging subscribers or users of the local area network or networks in connection with packets transmitted as transmission packets either through the local area network or through the bridge apparatus. Merely for simplicity of the description, it is possible to refer to a combination of local area networks and a bridge apparatus simply as a local area network. This is because the bridge apparatus is used in merely interconnecting the local area networks and because it is possible in general to refer to a plurality of devices collectively as a device.
A charging apparatus is already known for use in a router. In this conventional charging apparatus, source or originating addresses and destination addresses are identified in the network layer. Charges are accumulated in connection with the subscribers and in consideration of other data, such as distances of transmission of the packets and time periods used in communications.
Such a charging apparatus for the router is defective. This is because the charges are accumulated in connection with information available in the network layer. This conventional charging apparatus is therefore inoperative in the brouter.
It might be possible to remove the defect if the charges could be accumulated by identifying the subscribers by the use of addresses in the link layer, such as source addresses in the link layer. Such a source address is included in a header of an ethernet packet. Use should additionally be made of a destination address included in the header. The source and the destination addresses of the header are, however, used in a media access control (MAC) layer known in the art. As a result, the charging apparatus is again defective for the reasons which will be described in the following.
In the media access control layer, some of the packets are transmitted regardless of intentions of the subscribers, namely, without relation to communications intensionally exchanged among the subscribes. Such packets will herein be called particular packets. For example, host computers of the local area networks transmit and receive the particular packets in recognizing their network addresses in one another. Such a particular packet is formed in accordance with either an address or forward address resolution protocol (ARP) or a reverse address resolution protocol (RARP). It is undesirable to charge the subscribers for these particular packets.